Generally known fiber composite materials include glass fiber-reinforced resins produced by impregnating glass fibers with the resins. Such glass fiber-reinforced resins are generally opaque. However, Patent Documents 1 and 2 disclose methods for obtaining transparent glass fiber-reinforced resins by matching the refractive index of the matrix resin with the refractive index of the glass fibers impregnated therewith.
Patent Document 3 by the present applicants discloses that a highly transparent fiber composite material can be obtained by impregnating a so-called microfibrillated fiber material with a matrix material. Patent Document 3 proposes that fibers produced by fibrillating and grinding fibers derived from plants, such as pulp, and also bacterial cellulose having a three-dimensional structure and produced from a product containing bacteria and cellulose produced by the bacteria by removing the bacteria therefrom can be used as the microfibrillated fiber material.    [Patent Document 1] Japanese Patent Application Laid-Open No. Hei. 9-207234.    [Patent Document 2] Japanese Patent Application Laid-Open No. Hei. 7-156279.    [Patent Document 3] Japanese Patent Application Laid-Open No. 2005-60680.